Facebook’s revenue is soaring and the company’s coding wizards have shown Madison Avenue they understand smartphones. The next thing to prove: the magic won’t wear off soon.

Facebook reports fourth-quarter financial results Wednesday. The world’s largest social network is still growing, just not as quickly as in the past. The number of people who visit the site at least once a month grew 2.9% in the third quarter, compared with the previous quarter. That followed a string of 4% and 5% sequential increases. When you’re as big as Facebook, though, even a 2.9% increase amounts to 34 million additional regular users.

Investors are betting that earnings will grow 30% a year for the next three to five years, according to S&P Capital IQ. If user growth is slowing, Facebook must either charge more for each ad or sell more ads to each user, some who are potentially visiting other websites.

Facebook will announce its results after the market close and will hold a conference call for analysts at 5 p.m. ET. Analysts expect adjusted earnings of 27 cents a share, up from 17 cents a year ago, according Capital IQ. Revenue is projected to increase 49% year-over-year to $2.4 billion.

Here are some key areas to watch:

A Different Number: If user growth slows again, Facebook could face some worrying questions. But some experienced Facebook watchers have their eyes on another number: the share of “monthly active users” who log into the service every day.

That ratio has been climbing, to 61% in the third quarter, from 57% in 2012. Facebook is the only major social-media company that discloses this number, and that’s probably because the number looks so good.

Think of Facebook like a television show. People watch, they see ads. But unlike a half-hour sitcom, the Facebook show never ends. The longer people stay on, the more ads they see and the more detail about themselves they share with Facebook. Heavy Facebook users view it almost as a utility to communicate with friends and keep up with family news and events. The higher the ratio of daily users to monthly users, the more potential Facebook has to make money.

“Investors should pay attention to it,” said Mark Mahaney, an analyst for RBC Capital Markets, who expects the ratio to grow to 61.6%. “If that were to decline, that would be an issue.”

Getting Young Again: Facebook’s conference call last quarter included a bombshell: Its youngest teen users were using the service a little less.

That reversed what Facebook had said previously about teens leaving the service and opened the gates to a rash of speculation that the service was losing its cool. Could it implode like Friendster or Myspace?

Investors and advertisers mostly shrugged. Facebook shares are up 12% since that disclosure, far more than market indexes. Why? Two potential reasons: Teen users aren’t as valuable in advertising terms. And Facebook may have bought a $1 billion insurance policy on teens in 2012 when it acquired Instagram, which is still considered cool.

But some analysts think Facebook is also looking to build its own teen-friendly apps. Dan Slagen, senior vice president of marketing for Nanigans, a digital-marketing software company, pointed to Facebook’s stand-alone messenger app that has been gaining traction. “We might see more of those types of offerings,” he said.

First, there’s only a finite amount of space Facebook has to show ads on its service. As that space fills up, prices are going up and Facebook ads are getting expensive for advertisers.

Second: Facebook ads are limited to a diminutive box with a photo and a little bit of text. It’s not the way creative advertising and marketing folks like to see their brands showcased. But Facebook could use its vast database of user information to power advertisements in other arenas, where the ads look … well … prettier.

“What about powering ads on TV? What about printing ads in the Economist that comes through my mailbox rather than yours?” asks Forrester Research analyst Nate Elliott. “This is a big opportunity.”

Anything Facebook discloses about its plans for an ad network will be very important.

Moving Pictures, Moving Targets: Facebook began a limited test of video ads in December, starting with a movie trailer. The ads begin playing automatically, albeit on mute, in people’s feeds. Video ads are a major potential revenue stream that Facebook hopes to sell at a premium to big advertisers — sort of like a Super Bowl commercial.

Video advertising on Facebook still has some pitfalls, though. Unlike a YouTube ad, which people are forced to watch, Facebook users can simply scroll past the ad.

From an investor standpoint, Facebook can’t roll out these video ads fast enough. They represent the social network’s biggest opportunity to grab dollars away from TV programs that still own the mass market branding business.